Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 15, 1998
Publication Date: N/A
Interpretive Summary: Penicillin G is the residue most frequently found in tissues. However, specific methods are needed to identify and quantitate suspect residues. However, many published methods are suitable only for residues in muscle. Liver and kidney tissues are most frequently tested for residues by regulatory agencies. It is therefore important to have a confirmatory procedure which can be used with these tissues as well as with muscle. The present procedure can be used for analysis of tissues at or below levels of concern to regulatory agencies. It does not require the use of toxic derivatizing chemicals containing mercuric chloride. It can be used as part of multiresidue procedure suitable for determination of all B-lactam antibiotics.
A procedure previously described for determination of B-lactam antibiotics in milk was modified for use with tissues. Tissues were homogenized in water and the procedure for milk was followed (procedure I). Recovery of penicillin G in acetonitrile extracts of tissues was improved by addition of Et4NCl and, in some cases, pH adjustment. Liver and kidney were extracted directly with acetonitrile (procedure II) to avoid degradation o penicillin G in water homogenates. The acetonitrile extracts were concentrated by evaporation and filtered. For cleanup, an automated HPLC fractionation was used. The fraction corresponding to penicillin G was tested by a rapid screening test and, if positive, was analyzed by HPLC. For analysis, an Inertsil ODS-2 column was used with a mobile-phase of 0.0067M KH2PO4, 0.0033M H3PO4 - acetonitrile (68+32) with UV detection at 215 nm. For confirmation, an aliquot of the water homogenate (procedure I) was treated with B-lactamase prior to extraction. Recoveries were 75-90 percent with a detection limit of 5 ng/g.